Circuit interrupter



Jan, 25,1949. R. M. BENNETT CIRCUIT INTERRUPTER '=,V Insulation Insulation Filed July 21, 1945 IhVeT'TbOP Robert M. Bennett,

Insulation His Attorne Patented Jan. 25, 1949 CIRCUIT INTERRUPTER Robert M. Bennett, Birmingham Township, Chester County, Pa., assignor to General Electric Company, a corporation of New York Application July 21, 1945, Serial No. 606,374

My invention relates to improvements in circuit interrupters and more particularly to improvements in arc extinguishing devices for circuit breakers for controlling circuits carrying alternatin currents especially over a wide range in altitude as in certain aircraft installations.

The proposal to use on aircraft three-phase alternating current systems at the relatively high frequency of 400 cycles per second introduced many problems. Even though the voltage of the A.-C. systems is relatively low, 208 Y/l20, it is several times greater than the voltage of the 11-0. systems which have been used in aircraft. With the paucity of information available on the interruption of alternating currents at altitudes from ground level to 50,000 feet or more, some of those skilled in the art of circuit interruption contend that only compression type are interrupters can be used. Such devices, because of their weight and complexity, are not ideally suited for aircraft application. Tests indicate that the frequency is of little consequence in the matter of interruption. Wide range of altitude is the principal difficulty. At low altitudes, that is, relatively high atmospheric pressure, the cooling sheet on the arc is comparatively large because of the high density of the air. This materially reduces the cross section of the are because the more rapidly it is cooled, the smaller the cross section becomes. Also, because of the greater current density, the inherent loop expansion or selfblowout effect of the arc is more efiective with decrease in cross section of the arc. At high altitude or low atmospheric pressure, the cross section of the arc large, and since the current density is relatively small, the loop expansion efiect is reduced. Consequently, the arc is sluggish and difficult to move. In order satisfactorily to dissipate a high current density are of small cross section with an open arc chute, a certain measure of restriction of the arc is required so that it cannot escape from the chute before it is suficiently cooled. On the other hand, the sluggish, low current density arc of large cross section, which is difiicult to move, must not be unduly restricted or it will tend to hang before that restriction. It therefore becomes necessary to provide means which functions satisfactorily to extinguish arcs having 3 Claims. (Cl. 200147) structure and .at their top,

2 such diverse characteristics because of the altitude factor. Furthermore, such means must be relatively light in weight, relatively simple in particularly reliable in operation for use on aircraft and especially aircraft for fighting purposes.

An object of my invention is to provide for circuit interrupters an improved open type are extinguishing device which is effective in interrupting alternating currents over a wide range in altitude. Another object of my invention is to provide an improved arc extinguishing device which combines opposing arc chute plates open front and bottom edges with a nesting U-shaped magnetic blowout member having wide upwardly offset perforate flange portions embracing the arc chute plates and a relatively narrow magnetic web partially closing the lower part of the gap between the rear edges of the plates together with a magnetizing conductor looped around the web and interconnecting a stationary switch contact mounted between the plates in front of and adjacent the magnetic web and a terminal stud mountin head located behind a barrier closing the upper part of the gap so as to provide a concentrated and effective magnetic arc extinguishing structure that is very compact and lightweight. A further object of my invention is to provide an improved magnetic arc extinguishing device requiring a minimum of parts when combined with a specially-formed cooperating circuit breaker structure. These and other objects of my invention will appear in more detail hereinafter.

In accordance with my invention, I provide an open type are chute wherein two spaced plates of electrically insulating material are shaped to provide a converging or diminishing are discharging channel at the top. Also in accordance with my invention, I provide a magnetic blowout structure comprising a U-shaped magnetic member having upwardly offset flanged portions embracing the outer faces of the chute plates and whose web portion is relatively narrow and partially closes the lower part of the gap between the chute plates at their rear edge. Further in accordance with my invention, the lead-in conductor to a stationary contact resiliently mounted between the chute plates adjacent the web portion of the U-shaped member is looped around My invention will be better understood from,

the following description when considered in connection with the accompanying sheet or drawings, and its scope will be pointed out in the appended claims.

In the accompanying drawing, Rig. 1 is a side elevation, partly in section landpartly broken away, of an arc extinguishing device. embodying my invention; Fig. 2 is a side elevation of, the embodiment Of my invention shown inl igf 1; Fig. 3 is a front end elevation of the embodiment of my invention shown in Fig. l; and Fig. 4 is an exploded perspectiveof the embodiment of my invention shown in Fig.1.

In the illustratedfembodiment of my invention, I'have shown an arc'extinguishing device of the magnetic blowout type with an open arc chute comprising two spaced plates '1 and "2 of suitable electrically insulating material such, for example, as disclosed in United States Letters Patent 2,366,485, issued January 2, 1945 and assigned to the assignee of this invention. For magnetic blow out purposes, I provide around two sides and the rear edge of the arc chute a U '-sha'ped mag netic member which has,'in the vertical direction,relatively wide'upwardly offset'flange portions 3 and i contiguous to the outer parallel faces of the plates I" and 2 respectively, and a relatively narrow webjportion 5 across the gap betweenthe' plates at the rearbdge thereof,

For "best magnetic properties. and minimum weight, the flanges ahdweb the u shaped member a're'iorn'ied from one piece of suitable magnetic" material of uniform thickness, and

theflanges' are perforated so to provide substantially the same maghetic cross section as the 'web' portion '5 as shown more; clearly. in'FigQ Between the plates I and 2 and adjacent and in "front "or the web ortion 5 of then-sha ed member, I mount a relatively stationary con tact'ii'of suitable material which meets the re-.

quirements of low operating temperature, fhig h welding. current, short are duration a nd minimum contact deterioration For meeting these reqirements, I have found that a contact made of a sintered mixture of silver and tugsten is satis-' factory.

Cooperating with the relatively stationary contact 6 is a contact '5 mounted for. movement between the plates i and 2 near the lower edge thereof to engage the contact 6 and separable therefrom to interrupt a circuit within the chute formed by these plates. The arrangement by whichthe movable contact lis actuated to and from the closed circuit position is immaterial as far. asv my invention is concerned, but I have. illustrated part of a circuit breaker mechanism which is the subject matter of copending application. Serial No. 582,053,.filed March 10, 1945 by John A. Favre and assigned-to the assignee at high altitudes, the plates 5 of this invention. Thus, as shown, the contact I is mounted on a rigid current conducting arm 8. This arm is supported on a pin 53 mounted in a channel shaped carrier it which is supported on a suitably insulated member H carried by a shaft i2 so as to turn upon movement of the shaft. To the arm 8 is connected a flexible lead 53 which extends to the lower terminal, not shown, of the circuit breaker.

In accordance with my invention, I so mount the relatively stationary contact 6 in front of the web portion 5 of the U-shapeol member as to have an electric current conducting member such as a flexible lead i from a terminal stud l5. looped around the webportion and connected to the contact 5. Thus, as shown, contact ii is resiliently supported on leaf spring means It which is suspended from or secured to the terminal stud I?) by suitable means such as a rivet i1 passing through holes in the spring means and through holes in a stud plate head It secured. tothe stud l5 and a spacer plate l9. While some current may pass through the leaf spring means Edit is to be noted that only one leaf of. the spring is attached to the contact 6. The resistance of this spring, because of its small cross section, is such that only a very small fraction of current in the circuit breaker a Sh e oi. n a n m t al i w i h. omes down from between the stud plate l8; and. the spacer plate, i9 around the back of the web portion 5. between the conductor is and the web portion and around the front of the web portion between the leaf spring means It and the Web portion.

arccooling action before the arc passes out of the chute without preventing blowout of the arc and 2 are shaped to provide a converging arc discharging channel, the cross section of which will be most clearly obvious from Fig. 3. For this purpose, approximately the lower half of each of the plates land 2 is of uniform thickness and approxi-,

mately the upper half of these plates increases substantially uniformly in thickness at their adjacent faces to provide a converging are discharg ng channel. To prevent blowdown of the ;arc "below the stationary contact 6, I provide an insulating shield positioned below. the contact 6. This shield may conveniently. consist of two parts 2% and 2.2, as shown more clearly in Big. i, which are respectively molded on or As will be apparent from the exploded perspective of; Fig. 6, these projections 21! and E2 overlap, when as,- sembled as, Figs. 2 and 3, to provide underneath the contact 6 a continuous shield extending from the. back edge of the chute to in front of the contact 5 For maintaining the assembly of the. chute,

I provide at the front a rivet 23 whichpassesthrough openings 24 in the flanges 3 and; 6. of the U shaped member and through openings 25 in the. plates 4 and. 2, these latter openings,

being recessed to, receive a tubular spacer 2% ofsuitable insulating material through which, the rivet 23 also passes. For maintaining the assembly at the rear of the. chute, the flanges,

3 and l of the U.shaped member are provided with extendingears 2.7 which are. bridged by a. cross member 2a: of nonmagnetic material, suit-.. ably, secured to. theears 2-1. The, stud plate It.

is positioned in front of this bridging piece 28 and separated therefrom by an insulating spacer 29.

For looking the parts in position at the rear of the chute and also shielding the leaf spring means I 5, I provide a spacer member 3% of suitable insulating material which fits snugly between recessed portions 3! in the plates 1 and 2 and against the leaf spring means it and comes to rest with its projecting flanges 32 against the top edges of the plates I and 2. The shield 30 is provided with a recessed opening 33 for receiving the head of the rivet I]. The whole assembly is then secured to the insulating base 34 of the switch by securing the stud 15 to the base with a nut 35 and suitable Washers 36. For securing the lower edge of the chute firmly to the base 34, the plates 1 and 2 may be provided with downwardly projecting portions 37 which are abutted by the head of a T-shaped member 38 of suitable insulating material which is suitably secured to the base 34 as by a screw 39. In order to secure a firm wedging action at the top of the rear edge of the chute, the stud plate [8 is tapered at its lower end to fit snugly against correspondingly tapered shoulders 58 on the plates I and 2,

With the foregoing described arrangement of elements, when the current flows through the flexible lead l4, the U-shaped member is magnetized in such a way that the flux tending to pass between the sides 3 and 4 of the U-shaped member is in a direction tending to push the are upward in the chute by virtue of the joint magnetic action between the flux field around the arc and the transverse flux field between the flanges 3 and 4 of the U-shaped member. The are is thus rapidly distended, but at low altitudes it is unable to escape from the converging arc discharging channel until it is sufficiently cooled to be rapidly extinguished in the vicinity of the throat of this channel. On the other hand, at high altitudes where the arc is sluggish, there is a strong magnetic action tending to keep the arc moving and the cross section of the arc is reduced by the magnetic action which drives the arc into the converging channel where it is cooled sufficiently to be interrupted.

Because of the relatively light weight of the parts, particularly the magnetic blowout structure and also the compactness of the are quencher and the rigidity of the structure, circuit breakers embodying my invention are particularly adapted for use on aircraft over a wide range in altitude.

While I have shown and described my invention in considerable detail, I do not desire to be limited to the exact arrangement shown, but seek to cover in the appended claims all those modifications that fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an electric switch, an arc chute open at the top, front and bottom edges thereof comprising two oppositely spaced rectangular plates of electrically insulating material having an insulating barrier therebetween for closing substantially the upper half of the gap between the plates at the rear edge thereof, approximately the lower half of said plates being of uniform thickness and approximately the upper half of said plates increasing substantially uniformly in thickness at their adjacent faces to provide a. converging arc discharging channel at the top thereof, a U-shaped. magnetic member of uniform thickness having relatively wide upwardly ofiset perforated flange portions contiguous to the outer faces of said plates and a relatively narrow web portion of substantially the same magnetic cross section as each perforate flange across approximately the lower half of the ap between the plates at the rear edge thereof and provided with a non-magnetic mounting member interconnecting said flanges behind said barrier, a stud terminal head engaging said plates behind said barrier for clamping said non-magnetic member in mounting position, a contact, means resiliently mounting contact between said plates in front of and adjacent the web portion of said U-shaped member, an electric current conductor looped around said web portion from the rear to the front thereof and connected between said relatively stationary contact and said terminal head, and a cooperating contact mounted for movement between said plates near the lower edge thereof to engage said relatively stationary contact and separable therefrom to interrupt a circuit within the chute.

2. In an electric switch, an arc chute open at the top, front and bottom edges comprising two oppositely spaced rectangular plates of electrically insulating material having an insulating barrier closing the upper part of the gap between the rear edges thereof, a U-shaped magnetic member having upwardly offset flange portions embracing said plates and a relatively narrow web portion partially closing the lower part of the gap between the rear edges of said plates, a terminal stud having a mounting head engaging the plates behind said insulating barrier, a relatively stationary switch contact resiliently suspended from said head between said plates in front of and adjacent the web portion of said U-shaped member, a flexible electric current conductor extending from said terminal mounting head in a magnetizing loop around said web portion from the rear to the front thereof, said conductor being connected to said relatively stationary switch contact and terminating thereat, and a cooperatin movable switch contact mounted for movement between said plates near the lower edge thereof to engage said relatively stationary switch contact and separably therefrom to interrupt a circuit within the chute.

3. In an electric switch, an arc chute open at the top, front and bottom edges thereof comprising oppositely spaced rectangular plates of an electrically insulating material having the upper half of the inner walls thereof converging to form an upward discharge channel, an insulating spacer barrier mounted between said plates to close the gap between the rear edges of said converging walls, U-shaped magnetic member having upwardly offset perforate flange portions embracing said plates and a relatively narrow web portion of substantially the same magnetic cross section as each perforate flange partially closing the lower half of the gap between the plates at the rear edge thereof, a terminal stud having a mounting head engaging the plates behind the spacer barrier, a relatively stationary switch contact suspended from said head between said plates in front of and adjacent the web portion of said U-shaped member, and an electric current conductor extending from said terminal head in a magnetized loop around said web portion from the rear to the front thereof, said conductor being connected to said relatively stationary contact: and; terminated thereatr, and a cooperating Contact mounted formovement. between said plates near. the lower edga there..- of 15 engage said relatively stationary; contactand; Separably therefrom to interrupt a. circuit. wiiahin the chute.

ROBERT M; BENNETT;

REFERENCES CITEH' The follcwing references are of record. it the. fi'l'g of this patent:

STA'IES' PATENTS Name Date Reisbach: Apr; 2', 19-12 Evans Aug; 12, v 1919:

Tritla. Deci 6, 1921 

